In the past, many wheelchairs and other invalid assistance vehicles have been provided to assist in transporting non-ambulatory persons. In some of these vehicles, particularly invalid walkers, adjustable seats and side rails have been provided so that the walker may be adjusted to the particular size of the invalid. However, such adjustments normally are at least semi-permanent and remain in the adjusted position as long as the individual patient has need for the vehicle. Some examples of this type of structure are disclosed in U.S. Pat. Nos. 1,307,058 McGrath; 2,374,182 Duke; 2,459,066 Duke; 2,530,544 Schwantes; 2,792,052 Johannesen; and 2,866,495 Diehl et al.
Other prior art vehicles, particularly certain wheelchairs, are provided with a fixed frame supported by wheels and having a jack or the like for raising the seat of the vehicle so that the occupant of the vehicle may be positioned at a desired elevation. Some examples of this type of structure are disclosed in U.S. Pat. Nos. 2,546,765 McKinley; 2,609,862 Pratt; 2,915,112 Schwarz; 3,905,436 Karchak et al; 3,937,519 Schoolden; and 3,953,054 Udden et al.
In other prior art vehicles, such as that shown in U.S. Pat. No. 2,641,306 to Lerman, a wheelchair having a seat and back is provided which may be raised and lowered selectively by a jack and which may be collapsed when desired including when the wheelchair is occupied. In order to do this, the seat and back must be flexible since they are connected to the side frames. Also, even though the seat and back may be raised, the armrests remain fixed because they are integrally formed with the side frames. Accordingly, the occupant loses the sense of security offered by the armrests when the seat is elevated.